The invention concerns an antenna apparatus and an antenna array comprising at least one antenna apparatus.
In the semiconductor technology and/or the microsystem technology, thin wires are used for connecting and electrically contacting integrated circuits to other electric structures. The method used in this case is also referred to as wire bonding and the thin wires used are accordingly also referred to as bond wires. Thus, these bond wires mainly serve for creating a galvanic connection between two electrically conductive structures.
For example, integrated circuits (IC) may be galvanically connected by means of bond wires to structures at a substrate carrying the IC. With respect to integrated circuits, e.g., radio-frequency microchips which comprise antenna ports for linking antennas are known. The antenna ports form terminal regions for antennas and, at the same time, signal outputs by means of which a signal to be transmitted may be transmitted to the antenna linked thereto.
In this case, it is known to use bond wires as radiators, or antennas. For example, a bond wire connecting an antenna port of a microchip to an electrically terminating structure on a carrier substrate carrying the microchip forms an antenna. This type of antennas is also referred to as a bond wire antenna.
For example, such a bond wire antenna is described in US 2008/0291107 A1. Herein, an RF chip is connected to a bond pad on the substrate by means of bond wires. The RF chip comprises a differential antenna terminal, i.e., two antenna ports, a respective bond wire being linked to each respective antenna port. Furthermore, it is described that the two bond pads may be connected to an electrically conductive path on the substrate in order to realize a folded dipole structure. Due to the two differential antenna ports, the region forming the termination of the antenna is located on the chip in the antenna structure described in this Reference.
U.S. Pat. No. 7,768,456 B2 shows a similar structure. In this case, two bond wires linked to two differential antenna ports of the chip are also routed to bond pads arranged on the substrate. The two bond pads are also connected to each other by means of an electric conductor. This reference describes that a metallic plate is to be used for this connection. In order to ensure between the two bond pads a current flow as direct, or linear, as possible, the width of the metallic plate should be larger than the diameter of the bond wires.
Known RF chips usually comprise only two (differential) antenna ports so that a maximum of two bond wires may be used as antenna. FIG. 1A shows such a pin assignment of a known chip 1. The chip 1 comprises a first antenna port 2 and a second antenna port 3.
FIG. 1B shows a further example of the conventional technology. In this case, an above-mentioned chip 1 is arranged on a substrate 4. The substrate 4 comprises a first bond pad 5 and a second bond pad 6. A first bond wire 7 connects the first antenna port 2 of the chip 1 to the first bond pad 5. A second bond wire 8 connects the second antenna port 3 of the chip 1 to the second bond pad 6.
The above-mentioned known bond wire antennas have the advantage that the bond wires used for galvanically connecting may simultaneously be used a radiators or as antenna. Thus, separate antenna structures may be omitted.
However, it is difficult to adjust the antennas. This is especially the case for radio signals in the radio-frequency range having a wavelength in the millimeter range. Here, fluctuations of the antenna length in the range of a few millimeters or micrometers already lead to large deviations in the radiation performance of the antenna.
In principle, the wavelength of the radio signal to be emitted with the bond wire antenna is determined, among other things, by the length of the antenna, i.e., by the length of the bond wire stretched between the RF chip and the bond pad on the substrate. Usually, the bond pads are positioned on the substrate at defined locations of the substrate. The antenna ports at the RF chip are also positioned at defined locations of the chip. Thus, the distances between the antenna ports on the chip and the bond pads on the substrate are predefined and, furthermore, may significantly vary depending on the chip manufacturer or the substrate manufacturer, respectively. Additionally, during the chip bonding of the RF chip onto the substrate, deviations in the relative positioning with respect to each other may also occur, i.e., the manufactured chip-substrate arrangements are usually not one hundred percent identical to each other.
This means that tuning the length of the bond wire is subject to certain restrictions resulting from the above-mentioned positions of the bond pads relative to the antenna ports. For example, the bond wire has to invariably have a certain minimum length in order to be able to connect the antenna port with the bond pad on the substrate. However, this mechanically predefined minimum length of the bond wire does not have to match the length of the bond wire desired for tuning the bond wire antenna. Therefore, the length of the bond wire may not simply be adjusted to the desired wavelength of the radio signal without having to observe the given (e.g. mechanical) restrictions (e.g. minimum length).
On the other hand, a bond wire may not be arbitrarily long. Due to its very thin diameter, a bond wire tends to break with increasing length.
In practice, this makes it difficult to adjust the known bond wire antennas exactly to the desired wavelength of the radio signal to be emitted. Actually, an individual bond wire would have to be configured for each substrate-chip arrangement in this case. However, this would lead to unprofitable production costs. For this reason, the currently known machine-manufactured bond wire antennas sometimes have large fluctuations with respect to radiation characteristic, e.g., with respect to their antenna gain.